Process for maintaining temperature differential in coking chamber of horizontal coking oven

ABSTRACT

A process and apparatus for increasing the throughput of a horizontal byproduct coke oven. The coal charge in the coking chamber is subjected to a first elevated temperature in the intermediate zone between the top and bottom of the coking chamber. The coal charge in the bottom zone adjacent the base of the coking chamber is subjected to a second elevated temperature that is between 50* C. and 150* C. less than the first elevated temperature in the intermediate zone and the coal charge in the top zone adjacent the top of the coking chamber is subjected to a third elevated temperature that is about 100* C. higher than the temperature of the intermediate zone. With this process, a temperature gradient is maintained in the coal charge during the coking process with the lowest temperature adjacent the bottom and the highest temperature adjacent the top of the coal charge. The temperature gradient is obtained by either varying the thickness of the heating walls, providing high thermal conductivity refractory bricks for the portion of the heating wall adjacent the top of the chamber or modifying the burner arrangement or combustion process in the heating flues.

United States Patent [72] Inventors Victor Gobiet Wanne-Eickel; Gunther Juranek, Gelsenkirchen; Heinrich Schurhoff, Essen, all of Germany [21] Appl. No. 808,556 [22] Filed Mar. 19, 1969 [45] Patented Nov. 9, 1971 [73] Assignee Heinrich Koppers Gesellschait mit beschrankter Haftung Essen, Germany [32] Priority Mar. 27, 1968 [33] Germany [31] Pl77l044.0

[54] PROCESS FOR MAINTAINING TEMPERATURE DIFFERENTIAL IN COKING CHAMBER OF HORIZONTAL COKING OVEN 4 Claims, 5 Drawing Figs.

[52] U.S. Cl 201/44, 202/137, 202/139, 201/1 [51] Int.Cl ..Cl0b 21/20 [50] Field of Search 202/138, 139-144, 137,267, 223, 151; 201/44, 1

[56] References Cited UNITED STATES PATENTS 2,100,762 11/1937 Becker 202/143 2,839,453 6/1958 Becker 202/139 X 2,447,837 8/1948 Becker 202/138 2,498,784 2/l950 Becker 202/138 X Primary Examiner-Norman Yudkoff Assisran! E.raminerDavid Edwards Attorney-Standly J. Price, Jr.

ABSTRACT: A process and apparatus for increasing the throughput of a horizontal byproduct coke oven. The coal charge in the coking chamber is subjected to a first elevated temperature in the intermediate zone between the top and bottom of the coking chamber. The coal charge in the bottom zone adjacent the base of the coking chamber is subjected to a second elevated temperature that is between 50 C. and 150 C. less than the first elevated temperature in the intermediate zone and the coal charge in the top zone adjacent the top of the coking chamber is subjected to a third elevated temperature that is about 100 C. higher than the temperature of the intermediate zone. With this process, a temperature gradient is maintained in the coal charge during the coking process with the lowest temperature adjacent the bottom and the highest temperature adjacent the top of the coal charge. The temperature gradient is obtained by either varying the thickness of the heating walls, providing high thermal conductivity refractory bricks for the portion of the heating wall adjacent the top of the chamber or modifying the burner arrangement or combustion process in the heating flues.

HEIGHT ABOVE OVEN FLOUR, mm

TEMPE/i4 TUBE 6 TEMPEIM TURE IN MIDDLE 0F OVEN CH4 MBER PATENTEDNUV 9 I97! SHEET 2 OF 5 u. MES EGQQE 8 31 39 Q8 0% Q3 mow on 8 8m 3w QQM Ohm

PAIENTEDNUV 9 I971 3, 619.37 5

SHEET 3 [IF 5 PAIENTEDuuv 9 I971 SHEET 5 0F 5 6 6 6 L 0 2 3 5 6 W 5 0 8 7 9 9 6 7 4 4 5 4 2 H 6 8 6 7 6 2 7 5 2 9 r 9 u a a a .l

2 6 6 9 a 9 u U m 9 7 9 5 6 9 H U m 8 0 0 0 0 0 3 2 m Eu -W$Qqk EMAQ MAG? kIQPuI TIME AFTER CHARGING COAL hours MOISTURE CONTE/VT IN MIDDLE 0F OVEN CHAMBER K 3 HEAT/N6 FLUE TEMPERATURE l2006 PROCESS FOR MAINTAINING TEMPERATURE DIFFERENTIAL IN COKING CHAMBER OF HORIZONTAL COKING OVEN BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a process and apparatus for increasing the throughput of a horizontal byproduct coke oven by maintaining a vertical temperature gradient in the coal charge during the coking process and more particularly to a process and apparatus for improving the throughput of a horizontal byproduct coke oven by maintaining the temperature of the coal charge in an intermediate zone above the temperature of the coal charge adjacent the base of the coking chamber.

2. Description of the Prior Art The horizontal byproduct coke ovens include a coking chamber with heating chambers on opposite sides thereof. The walls separating the coking chamber from the heating chamber are generally referred to as heating walls. The heating chambers are compartmented into heating flues by transverse dividing walls and burners are provided in the heating flues to supply heat to the heating walls. The heat is transferred from the heating walls to the coal charge in the coking chamber during the coking process. The conventional horizontal byproduct coke oven has burners in the base of the flues that supply the greatest amount of heat to the heating walls adjacent the base of the coking chamber. Thus, with this arrangement, there is a temperature gradient vertically throughout the coal charge wherein the coal charge has its highest temperature adjacent the base of the coking chamber. In tall ovens wherein the burners at the base of the flue did not uniformly heat the coke oven wall, auxiliary high burners are provided to supply additional heat to the heating walls at an elevated location. With these byproduct coke ovens it was believed, in the past, that optimum coking of the coal charge was obtained when the heating walls were heated uniformly. It has been discovered that the quality of the coke and yield of the byproducts can be improved and the coking cycle substantially reduced by nonuniformly heating the coal charge in the coking chamber.

SUMMARY OF THE INVENTION The hereinafter described invention relates to a process and apparatus for providing a vertical temperature gradient in the coal charge during the coking process. The coal in an intermediate zone is subjected to a first elevated temperature, the coal charge in the lower zone is subjected to a second elevated temperature that is less than the first elevated temperature and the coal charge in the upper zone is subjected to a third elevated temperature that is greater than the temperature to which the coal is subjected in the intermediate zone. The temperature differential or gradient between the various vertical zones of the coal charge is maintained during the coking process. The temperature gradient in the coal charge may be obtained by either varying the thickness of the heating walls, providing high thermal conductivity refractory bricks for the ortion of the heating wall adjacent the top of the chamber, modifying the burner arrangement in the heating flues or modifying the combustion process within the heating flues.

Accordingly, the principal object of this invention is to provide a process and apparatus for coking coal in a horizontal byproduct coke oven wherein a vertical temperature gradient is maintained in the coal charge during the coking process.

Another object of this invention is to provide a process and apparatus for reducing the condensation of volatilized constituents in the coal charge in the intermediate zone of the coal charge.

A further object of this invention is to minimize the cracking of certain of the volatile constituents above the top of the coal charge.

'l'husc and other objects and advantages of this invention will be more completely disclosed and described in the following specification, the accompanying drawings and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1, 2 and 3 are graphical representations of the vertical temperature profile of the coal charge in a conventional coke oven during various stages of the coking process.

FIG. 4 is a graphical representation similar to FIGS. 1, 2 and 3 illustrating the temperature profile of the coal charge during the coking process as practiced in accordance with the hereinafter described invention.

FIG. 5 is a graphical representation illustrating the moisture content at various elevations in the coking chamber during the coking process.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the coking process, a coal charge is introduced into the coking chamber and the walls of the coking chamber are heated and the heat is transferred to the coal charge within the coking chamber. As the coal is heated, volatile constituents are volatilized and coke is formed. A charge is considered as being completely coked when it has attained a temperature of about 950C.-l000 C. throughout the entire charge. The optimum coking process includes essentially uniform heating throughout the entire charge. This includes both the length of the coking chamber, where there should be a slight increase in heating flue temperature from the machine side to the coke side that corresponds to the taper of the chamber, and also to the height of the coal charge within the oven chamber. As illustrated in FIGS. 1-3, a vertical temperature gradient of the coal charge in a conventional coke oven chamber clearly indicates that the coal charge is not unifonnly heated. For example, referring to FIG. 3, after the coal charge has been heated for approximately 8.5 hours, the temperature of the coal charge adjacent the bottom of the coking chamber, i.e. at 300 mm. above the coking chamber floor, was about 650 C. Progressing upwardly through the coal charge, it was observed at an intermediate zone, i.e. about 2,000 mm. above the chamber floor, the temperature had decreased to about C. From this intermediate zone the temperature of the coal charge gradually increased so that adjacent the top of the oven the temperature was about 400 C. After about 12.5 hours of heating, the coal charge adjacent the base of the oven attained a temperature of about l,000 C. The intermediate portion of the coal charge had attained a temperature of 2 50 C. The top portion of the coal charge had attained a temperature of about 500 C. The reduced temperature in the intermediate zone remains even up to about 16.5 hours of heating.

Referring to FIG. 2, a similar temperature differential between the lower zone adjacent the base of the oven chamber and the intermediate zone is apparent by the temperature curves. In FIGS. 2 and 3, the location of the zone where the sharp temperature differential exists is slightly higher in the coking chamber. It is, however, apparent in FIGS. 1-3 that the coal charge has not been heated uniformly and there is a definite lag in heating the intermediate zone of the coal charge. For convenience, throughout the specification and claims the vertical profile of the coke oven chamber shall be referred to as having a bottom zone, which is a zone adjacent the base of the coking chamber, an upper zone adjacent the top of the oven and an intermediate zone between the top zone and the bottom zone.

As indicated in FIGS. 2 and 3, the height of the various zones may vary with the different types of byproduct coke ovens. An evaluation of the results obtained and graphically illustrated in FIGS. 1-3 indicated that the temperature of the coal charge in the intermediate zone lagged considerably in the intermediate zone. A higher temperature was always measured in the lower zone of the coking chamber near the floor of the oven and also in the upper zone adjacent the gas collecting space. The temperature lag at the intermediate zone indicates the rate of coking in the intermediate zone is retarded in comparison with both the bottom zone and top zone. In order to complete the coking process, it is necessary to continue to heat the coal charge until the intermediate zone attains a temperature of between 950 C. and 1,000 C. Until this temperature is attained throughout the charge, the coking process is not complete and the charge cannot be pushed. To continue to heat the entire charge until the intermediate zone attains the temperature of 950 C. to 1,000" C. lengthens the coking time frequently by a period of several hours. The uneven temperature of the coal charge along the height of the coking chamber cannot be attributed to specific features of particular byproduct coke ovens. Differences in oven systems, heating flue temperatures, types of coal in the charge and the combustion gas supplied to the heating flues may shift slightly the height at which the temperature of the coal charge in the intermediate zone lagged from the temperature of the coal in the other zones or reduced the magnitude of the temperature differential between the various zones. It was determined, however, that all of the present ovens tested exhibited this reduced temperature of the coal in the intermediate zone of the charge when compared with the temperatures adjacent the bottom and top of the coal charge.

As illustrated in FIG. 5, it was further determined that the moisture content of the coal charge was somewhat higher at the locations where the temperature of the coal was below that of coal at other locations within the charge. In certain cases, the difference in the moisture content amounted to about 6 percent. It is believed the high moisture content in the locations where the temperature is below the remaining coal in the charge can be attributed to the following. Water is first vaporized by the increase of the temperature in the lower zone of the coke oven charge. The low boiling hydrocarbons are vaporized next and thereafter the higher boiling hydrocarbons are vaporized at progressively increasing temperatures. The vapors, i.e. water vapor, and the volatile hydrocarbons condense in the adjacent intermediate and colder zone of the oven charge as the vapors move upwardly through the oven charge. The condensation of these vapors in the intermediate zone requires a greater amount of heat to again vaporize the condensed volatile materials and this, it is believed, results in the temperature lag in the intermediate zones and thus delays the coking process. It will be apparent that the vaporization and condensation can take place in several stages within the coke oven chamber depending upon the height of the chamber and the height of the coke oven charge. The above theory is substantiated, we believe, by the observation of nests or agglomerates of uncoked coal and tarry components. The agglomerates could only have been formed by subsequent condensation of previously vaporized high boiling volatile constituents.

It has been discovered that it is now possible to obtain uniform coking of the coal charge along the height of the coal charge by adjusting the heat of the oven chamber and the coal charge therein differently at different heights according to the particular requirements. The heat of the oven chamber and coal charge therein should be increased at the height or heights at which the content of condensable substances is highest because of the partial condensation of volatile substances volatilized in lower zones. Suitable uniform heating can be obtained by reducing the temperature of the lower zone between about 50 C. and 150 C. below the temperature of the intermediate zone and advancing the temperature of the upper zone at least above l00 C. above the temperature of the charge in the intermediate zone.

As previously discussed, when the temperature in the bottom zone is above the temperature in the intermediate zone, the coking process is retarded in the intermediate zone. It has been discovered, however, that an increase of the temperature in the upper zone is advantageous, not necessarily from the standpoint of oven throughput but from the standpoint of improving the gaseous hydrocarbons recovered during the coking process. Where the temperature in the upper zone as compared with the intermediate zone is increased by at least I00 C., solid carbonaceous residue from the volatile constituents is not formed in the gas collecting portion of the coking chamber above the coking charge. In a coking process where the flue temperature was at l,380 C. and a pressure of 5 mm. in the gas collecting main and having a coal charge containing 29 percent volatile matter, carbonaceous residue could barely be detected in the gas collecting space above the coke charge, after the coke charge was pushed. This is the opposite of what occurs in coke ovens where the temperature in the upper zone lags behind the temperature in the lower portion of the coal charge. It is believed that the absence of the solid carbonaceous residue in the gas collecting space may be attributed to a proportionately lower amount of the vaporized hydrocarbons cracking and carbonizing in the gas collecting space and carbonizing within the upper portion of the coke charge because of the increased temperature.

Another advantage of this invention is an increase in the amount of aromatic compounds recovered in the vaporized hydrocarbons. For example, it was discovered by practicing the process of this invention that the amount of aromatic hydrocarbons in the vaporized product increases from 63 percent to 73 percent and the proportion of nonaromatic compounds is reduced by about 50 percent. This increases substantially the value of the gaseous product obtained by the coking process in that it contains more aromatic compounds and can be processed less expensively.

It has been further discovered by coking the coal charge in accordance with this invention that the strength of the pushed coke is increased to thereby increase the quality of the coke. The coke is formed in large agglomerates and small pieces of coke, i.e. coke breeze, is reduced.

Referring to FIG. 4, there is illustrated a temperature gradient as measured in a coking chamber after adjustments of the heating of the coke charge have been made in accordance with the herein described invention. After about l0 hours of heating, the temperature profile between the base of the coking chamber and a location of 1,305 mm. from the base of the coking chamber is at a temperature of about 150 C. In the intermediate zone, i.e. between 1,300 and 2,900 mm. from the base of the oven, the temperature is about 200 C. In the upper zone of the chamber, the temperature increases to about 300 C. The same temperature profile is substantially maintained through the coking process and the entire coke charge after 15 hours attains a temperature greater than l,000 C. indicating that the charge is completely coked.

In FIG. 2, for comparison, after 16% hours, the intermediate zone of the coal charge has not attained a temperature of 800 C. and the upper zone has attained a temperature of 900 C., whereas the lower zone has attained a temperature of about l,l00 C. The comparison of the temperature profiles of FIGS. 2 and 4 clearly illustrate how the throughput of the coking process is increased by reducing the time required for a complete coking cycle from a period in excess of 17 hours to 15 hours. The heating flue temperature in the heating chamber of the coke oven from which the data of FIG. 4 has been obtained was about 1,200 C. and the moisture content of the coal charge was 8.5 percent.

The apparatus suitable for carrying out the above described process can include alterations or modifications to a byproduct coke oven that will provide the desired temperature gradient to the coal charge, as previously discussed. It is, for example, possible to construct a horizontal byproduct oven with the heating walls of the oven chamber decreasing from the bottom to the top so that more heat will be trans ferred through the walls adjacent the top of the furnace. The heating walls may also be modified to provide a refractory material having a higher thermal conductivity in the upper region of the walls so that a greater amount of heat is transmitted through the walls adjacent the top portion of the coal charge. The burner arrangement can be modified by positioning the combustion nozzles for the low burners higher than conventional nozzles, as, for example, at a height between and 500 mm. above the floor or base of the coking chamber.

The combustion process Where high and low burners are utilized may be varied to supply excess air to the high burners and excess combustion gas to the low burners so that higher temperatures are generated adjacent the top portion of the coking chamber and combustion continues to take place in the passageways connecting groups of flues on opposite sides of the coking chamber.

According to the provisions of the patent statutes, the principle, preferred construction and mode of operation of this invention have been explained and what is considered to represent its best embodiment has been illustrated and described.

We claim:

1. A process for coking coal in a horizontal byproduct coke oven having a horizontal coking chamber in which said coking chamber has a lower zone adjacent the base of the coking chamber, an upper zone adjacent the top of the coking chamber and an intermediate zone between said lower zone and said upper zone comprising,

introducing a coal charge into said coking chamber,

subjecting said coal charge in said intermediate zone so that the coal charge is at a first predetermined elevated temperature,

subjecting said coal charge in said lower zone to a second predetermined elevated temperature such that the coal charge is between 50 C. and 100 C. less than said first predetermined elevated temperature,

subjecting said coal charge in said upper zone to a third predetermined elevated temperature so that the coal charge is at least C. higher than said first predetermined temperature in said intermediate zone, maintaining a temperature differential between said coal charge in said intermediate zone, upper zone and said lower zone while said coal charge is heated and converted to coke, and maintaining a temperature differential between the coal charge in said lower zone and the coal charge in said upper zone of between at least about C. and 200 C. 2. A process for coking coal in a horizontal byproduct coke oven as set forth in claim 1 which includes,

providing heating walls on opposite sides of the coking chamber in which the thickness of the heating walls decreases from the bottom to the top of the coking chamber. 3. A process for coking coal in a horizontal byproduct coke oven as set forth in claim 1 which includes,

providing refractory heating walls on opposite sides of said coking chamber in which the thermal conductivity of the refractory in the upper zone of the coking chamber is greater than the thermal conductivity of the refractory in the lower zone of the coking chamber. 4. A process for coking coal in a horizontal byproduct coking oven as set forth in claim 1 which includes,

providing heating chambers on opposite sides of said coking chamber and elevating the combustion gas inlet between about 100 mm. and 500 mm. above the base of the coking chamber. 

2. A process for coking coal in a horizontal byproduct coke oven as set forth in claim 1 which includes, providing heating walls on opposite sides of the coking chamber in which the thickness of the heating walls decreases from the bottom to the top of the coking chamber.
 3. A process for coking coal in a horizontal byproduct coke oven as set forth in claim 1 which includes, providing refractory heating walls on opposite sides of said coking chamber in which the thermal conductivity of the refractory in the upper zone of the coking chamber is greater than the thermal conductivity of the refractory in the lower zone of the coking chamber.
 4. A process for coking coal in a horizontal byproduct coking oven as set forth in claim 1 which includes, providing heating chambers on opposite sides of said coking chamber and elevating the combustion gas inlet between about 100 mm. and 500 mm. above the base of the coking chamber. 